The present invention relates to an extracorporeal circulation apparatus used for various treatments in the medical field related to a mammal and especially a human, and particularly to a novel extracorporeal circulation apparatus which is usable for a case in which a selected part of a body is to be kept at a predetermined (or preset) temperature by the xe2x80x9cselective temperature controlling (or adjusting) methodxe2x80x9d such as the xe2x80x9cselective cooling methodxe2x80x9d or the xe2x80x9cselective warming method.xe2x80x9d The apparatus of the present invention will be explained hereinafter with an example in a case of a human, but it is understood that the present invention is applicable to any mammal.
Since Woodhall introduced in 1960 a systemic profound hypothermia under a cardiac arrest for the purpose of protecting a brain against a hemorrhage or an ischemia upon a craniotomy, the systemic profound hypothermia has been employed in many types of operations. However, a pump-oxygenator employed in this method makes the procedure complicated and the blood perfusion to various organs insufficient and the method requires a large amount of heparin as an anticoagulant, resulting in problems such as a secondary cerebral hemorrhage.
One of the inventors has made an effort to overcome the problems mentioned above and has developed a method for cooling a brain selectively (which is substantially the same in its meanings as the abovmentioned xe2x80x9cselective cooling methodxe2x80x9d) while using a pump-oxygenator, and applied the method to a craniotomy (see J. Neurosurg; Vol 24, pages 993 to 1001, 1996). This selective cooling method did provide a cerebral hypotension of the brain safely, but still involved the problems with regard to the intra- and post-operative hemorrhages due to the use of a large amount of heparin still associated therewith.
In order to overcome these problems, one of the inventors discovered a method for injecting a cooled lactated Ringer""s solution as a fluid replacement (or a replenisher liquid) into a cerebral artery so as to cool only a brain exclusively and to dilute a blood simultaneously while cooling the blood, resulting in a substantially reduced heparin level, whereby reducing the risk of the hemorrhage (see Neurosurgery; Vol 31, pages 0149 to 1054, 1992). This method allows a reversible extreme hypotension to be established without undergoing an oxygen deficit and enables an extreme reduction in the amount of heparin to be used as a result of introduction of the cooled fluid replacement, whereby allowing the amount of heparin to be close to that used in an ordinary angiography. In addition, the introduction of the diluted blood into a lesion leads to various safety-improving effects such as reduction in blood loss.
As described above, since the brain temperature is lowered by injecting the cooled lactated Ringer""s solution. However, an amount of the lactated Ringer""s solution to be injected is generally large, the injection of the lactated Ringer""s solution dilutes the blood excessively and an amount of circulating blood is increased which results in the excessive body fluid condition, so that keeping the low temperature condition for a long time becomes difficult. Therefore, there is a problem in that a satisfactory low blood pressure condition (or cerebral hypotension) of the brain is not ensured. In addition to this, other problems may be occur: for example a large amount of low temperature diluted blood fills the body and a body temperature is lowered, a blood activity is lowered, balancing electrolytes in the blood becomes required, and an excessive overhydration condition may occur which cannot be attended at all with a diuretic drug.
Thus, one of the inventors studied the above problems extensively and proposed an extracorporeal circulation apparatus, which comprises (1) a fluid replacement supply unit which cools a fluid replacement (or a diluent or a replenisher liquid) and quantitatively injects the fluid replacement into a blood vessel (and thus into a body), (2) a blood concentration unit which quantitatively withdraws blood diluted by the fluid replacement from a blood vessel (and thus from the body) and concentrates the withdrawn diluted blood, and (3) a blood supply unit which quantitatively injects the concentrated blood into a blood vessel. Details of this apparatus is disclosed in Japanese Patent Kokai Publication No.9-290021. It is noted that the disclosure of the Publication is incorporated herein by the reference thereto. Using such extracorporeal circulation apparatus allows the selective cooling method to be carried out effectively.
In order to carry out the selective cooling method more smoothly, the present inventors have further studied the extracorporeal circulation apparatus which has been already proposed as described above, and have found that it is necessary for the more effective selective cooling method to more precisely control a temperature of an object which is a part of a body and to which the selective cooling method is applied (or a region of the body such as an organ, for example a brain, which is also referred to as merely xe2x80x9cobjectxe2x80x9d), and that it is important for such precise temperature control to measure a temperature of the diluted blood which is withdrawn from the interior of the body and control a temperature of the fluid replacement which is to be supplied into the interior of the body based on the measured temperature of the diluted blood when the extracorporeal circulation apparatus as described above is used, whereby the inventors have completed the present invention. That is, it has been found that the temperature of the object to which the selective cooling method is applied is more precisely controlled by measuring the temperature of the diluted blood which is withdrawn from the inside of the body and controlling the temperature of the fluid replacement which is to be supplied into the inside of the body based on the measured temperature of the diluted blood, whereby the selective cooling method is carried out more effectively.
In addition, there is a case in which it is desirable to warm an object to a predetermined temperature depending on a treatment for the object (i.e. a case of a selective warming method), and it has been found that when the object is, not cooled as described above, but warmed, the object to which the selective warming method is applied is more precisely controlled by controlling the temperature of the fluid replacement which is to be supplied into the inside of the body based on the measured temperature of the diluted blood, whereby the selective warming method is carried out more effectively.
That is, it has been found that when an selective temperature controlling method is applied in which a temperature of an object which is a part of a body is controlled to a predetermined temperature depending on a treatment for the object, the temperature of the object to which the selective temperature controlling method is applied is more precisely controlled by measuring the temperature of the diluted blood which is withdrawn from the interior of the body and controlling (or adjusting) the temperature of the fluid replacement which is to be supplied into the interior of the body based on the measured temperature of the diluted blood, whereby the selective temperature controlling method is carried out more effectively. The application of the present invention to the selective temperature controlling method will be explained hereinafter with reference mainly to the selective cooling method as an example. Since the selective warming method can be generally carried out substantially similarly to the selective cooling method except that the object is warmed in the selective warming method, those skilled in the art would readily apply the apparatus according to the present invention to the selective warming method based on the example of the selective cooling method.
It should be noted that in the extracorporeal circulation apparatus of the prior art which can be applied to the selective cooling method as described in Japanese Patent Kokai Publication No. 9-290021, the temperature measurement of the withdrawn diluted blood is not considered at all. Further, the Publication suggests that a temperature of a fluid replacement itself which is to be supplied to the interior of the body is controlled to a preset temperature by a heat exchanger through which the fluid replacement is passed depending on a temperature to which the object is to be cooled, but the temperature of the withdrawn diluted blood is not considered at all as to the temperature control of the fluid replacement. Such control of the prior art supplies the fluid replacement which has been controlled to the temperature by the heat exchanger beforehand irrespective of a condition of the object to which the selective cooling method is being applied. However, the condition of the object to which the selective cooling method is applied may change momentarily, which results in that the temperature of the object deviates from a predetermined temperature at which the object is to be kept, so that the temperature of the withdrawn diluted blood may change. For example, an organ as the object swells up and its temperature rises, and thereby the temperature of the withdrawn diluted blood may rise. In such case, in order to decrease the temperature of the organ as the object to the originally predetermined temperature so as to carry out the selective cooling method, it is necessary to lower the temperature of the fluid replacement to be supplied so as to suppress the temperature increase of the organ itself, and vice versa.
However, since the extracorporeal circulation apparatus of the prior art as described above does not take the temperature of the withdrawn diluted blood into consideration, it cannot be adapted to the condition change of the object of the selective cooling method, and thus the change of the diluted blood temperature, whereby there may be a problem in that the selective cooling method cannot be applied properly. The present invention solves such a problem.
That is, the present inventors have found that by measuring the temperature of the diluted blood which is withdrawn from the interior of the body and controlling the temperature of the fluid replacement which is to be supplied into the interior of the body based on the measured temperature of the diluted blood, the temperature control of the object to which the selective temperature controlling method such as the selective cooling method or the selective warming method is applied is carried out more precisely, so that the selective temperature controlling method is carried out more effectively.
It is noted that depending on a kind of the object to which the selective temperature controlling method is applied and a kind of treatment for the object (such as an operation, a maintenance of a low active condition or the like), a temperature at which the object is to be kept (for example, a temperature to which the object is to be cooled, or a temperature to which the object is to be warmed), namely the predetermined temperature of the object is determined upon the application of the selective temperature controlling method using the extracorporeal circulation apparatus. Therefore, the predetermined temperature at which the object is to be maintained by means of the selective temperature controlling method as well as an accuracy of such temperature maintenance is properly selected by for example a doctor depending on the treatment for the object.
Then, in the first aspect, the present invention provides an extracorporeal circulation apparatus used for the selective temperature controlling method (for example the selective cooling method and/or the selective warming method) in which a temperature of an object which is a part of a body is kept (or shifted (or changed) and kept) at a predetermined temperature (T0), which apparatus comprises:
(A) a fluid replacement supply unit which quantitatively supplies (or meters) a fluid replacement of which temperature has been adjusted into a blood vessel (thus into an interior of the body);
(B) a blood concentration unit which quantitatively withdraws (thus removes) blood diluted by the fluid replacement from a blood vessel (thus from an interior of the body) and concentrates the withdrawn diluted blood; and
(C) a blood supply unit which controls a temperature of the blood which has been concentrated and quantitatively supplies (or meters) the concentrated blood into a blood vessel (thus into an interior of the body),
the blood concentration unit comprising a diluted blood temperature sensor which measures a temperature of the withdrawn diluted blood, and the fluid replacement supply unit comprising a means which controls (or adjusts) a temperature of the fluid replacement to be supplied based on a different extent between the measured diluted blood temperature (T1) and the predetermined temperature of the object (T0) (such as a difference xcex94T (=T1xe2x88x92T0), a ratio TR (=T1/T0) or the like). It is noted that the means which controls the temperature of the fluid replacement to be supplied serves to make the different extent smaller.
By means of the apparatus as described above, the control to keep the object to which the selective temperature controlling method is applied at a temperature which is close to the predetermined temperature, and preferably substantially the predetermined temperature can be carried out more accurately, so that the selective temperature controlling method can be carried out more effectively compared with using the prior art apparatus.
In the apparatus of the present invention, the diluted blood which is withdrawn out is discharged from the object to which the selective temperature controlling method is applied, and therefore it is assumed that the temperature of the diluted blood measured by the diluted blood temperature sensor (T1) represents the temperature of the object to which the selective temperature controlling method is applied. The term xe2x80x9crepresent(s)xe2x80x9d herein is intended to mean that the temperature of the diluted blood is not necessarily the temperature of the object itself (although it is preferably the temperature of the object itself), variation of the diluted blood temperature or the diluted blood temperature being relatively higher or lower corresponds to variation of the object temperature or the object temperature being higher or lower. Particularly, when the predetermined temperature at which the object is to be maintained or the accuracy of the temperature maintenance at the predetermined temperature is not so strict, the above assumption is conveniently applicable.
Further, when a supply rate of the fluid replacement is large depending on the treatment which is applied to the object so that a withdrawal rate of the diluted blood is large, a temperature change of the diluted blood during a period from the object to the diluted blood temperature sensor, and in particular a temperature change due to the body temperature may be neglected since the period required for the diluted blood to flow from the object to the outside of the body becomes short. In such case, it is often that the temperature of the withdrawn diluted blood (T1) is regarded as the temperature of the object at that time which is to be kept at the predetermined temperature (T0).
In the apparatus of the present invention, the xe2x80x9cmeans which controls a temperature of the fluid replacement to be supplied based on a different extent between the measured diluted blood temperature (T1) and the predetermined temperature of the object (T0)xe2x80x9d is a means which obtains the different extent (such as a difference or a ratio) between the measured diluted blood temperature and the predetermined temperature of the object, and increases or decreases the temperature of the fluid replacement to be supplied based on the different extent. It is noted that when there is substantially no different extent, the means keeps the temperature of the fluid replacement as it is.
Concretely, when the diluted blood temperature (T1) is higher than the predetermined temperature of the object (T0) (that is, when T1xe2x88x92T0 greater than 0 or T1/T0 greater than 1, and thus for example when cooling by means of the fluid replacement seems to be insufficient in the case of the selective cooling or when warming by means of the fluid replacement seems to be excessive in the case of the selective warming), the above means functions to decrease the temperature of the fluid replacement to be supplied. Such function can be achieved by forming a control system which obtains the different extent between the diluted blood temperature (T1) and based on the different extent the predetermined temperature of the object (T0) and warms and/or cools the fluid replacement to be supplied into the inside of the body so as to make the different extent smaller. The formation of such system is well known in the field of the temperature control. For example, a manner can be employed in which a set temperature of a heat exchanger (or a warming/cooing device) which controls the temperature of the fluid replacement supplied into the inside of the body is changed (that is, the set temperature is lowered) depending on the measured temperature. Also, when the diluted blood temperature (T1) is lower than the predetermined temperature of the object (T0) (that is, when T1xe2x88x92T0 less than 0 or T1/T0 less than 1, and thus for example when cooling by means of the fluid replacement seems to be excessive in the case of the selective cooling or when warming by means of the fluid replacement seems to be insufficient in the case of the selective warming), the above means functions to increase the temperature of the fluid replacement to be supplied.
It is noted that when there is substantially no different extent (that is, when T1xe2x88x92T0=0 or T1/T0=1, and thus for example when the selective temperature controlling method seems to be working satisfactorily), the above means functions to keep the temperature of the fluid replacement to be supplied at that time.
In a case where the temperature of the blood diluted by the fluid replacement may change after it has once reached a temperature which is the same as that of the object in the object, the above explanations are not applicable. Also, in a case where the blood diluted by the fluid replacement is withdrawn without its temperature having been thermally equilibrium with the object because of a short residence time of the fluid replacement in the object since a supply rate of the fluid replacement is too large (especially at the beginning of the fluid replacement supply), the above explanations are not applicable. If no change in T1 when the supply rate of the fluid replacement is temporarily increased and/or decreased a little, the above explanations will be applicable. It is preferable to follow the supply rate which is described concretely in the xe2x80x9cDetailed Description of the Inventionxe2x80x9d part of the present specification.
Alternatively, when the supply rate of the fluid replacement into the inside of the body may be changed depending on the treatment for the object, it is also possible to use a means which changes the supply rate of the fluid replacement into the inside of the body in place of or in addition to the above means which adjusts the temperature of the fluid replacement. That is, it is utilized that an amount of heat transferred from the fluid replacement to the object or from the object to the fluid replacement changes when the supply rate of the fluid replacement is changed. Generally, when the supply rate is increased, an amount of heat transferred is increased. That is, when the temperature of the fluid replacement is lower than that of the object, the object is further cooled by the increase of the supply rate of the fluid replacement. Also, when the temperature of the fluid replacement is higher than that of the object, the object is further warmed by the increase of the supply rate of the fluid replacement, and when the supply rate of the fluid replacement is decreased, reversed phenomena are observed. This embodiment to change the supply rate is particularly preferably used for changing the temperature of the object a little.
In the second aspect, the extracorporeal circulation apparatus according to the present invention comprises a supplied fluid replacement temperature sensor in addition to the diluted blood temperature sensor, and the former sensor measures a temperature of the fluid replacement which is supplied to the inside of the body (a supplied fluid replacement temperature, T2). In this apparatus, an averaged value (Tav, an averaged temperature such as an arithmetical mean, a logarithmic mean, a weighted mean or the like) of the supplied fluid replacement temperature (T2) and the diluted blood temperature (T1) is assumed to be represent the temperature of the object to which the selective temperature controlling method is applied in place of the diluted blood temperature (T1) in the apparatus of the first aspect, and a different extent between the averaged temperature (Tav) and the predetermined temperature of the object (T0) is taken into consideration in place of the different extent between the diluted blood temperature (T1) and the predetermined temperature of the object (T0) in the apparatus of the fist aspect. The temperature of the fluid replacement to be supplied is controlled so that such former extent becomes smaller. The other features are substantially the same as those of the apparatus of the first aspect.
Thus, in the apparatus of the second aspect, the xe2x80x9cmeans which controls a temperature of the fluid replacement to be supplied based on a different extent between the measured diluted blood temperature (T1) and the predetermined temperature of the object (T0)xe2x80x9d in the apparatus of the first aspect is a means which obtains the different extent between the predetermined temperature of the object and the averaged temperature of the diluted blood temperature and the supplied fluid replacement temperature, and increases or decreases, or keeps the temperature of the fluid replacement to be supplied based on thus obtained different extent. That is, the different extent between the predetermined temperature and the diluted blood temperature is considered while further considering the supplied fluid replacement temperature. Similarly to the apparatus of the first aspect as described above, the supply rate change of the supplied fluid replacement may be applied in place of or in addition to the control of the fluid replacement temperature.
Concretely, when the averaged temperature (Tav) is higher than the predetermined temperature of the object (T0) (that is, when Tavxe2x88x92T0 greater than 0 or Tav/T0 greater than 1, and thus for example when cooling by means of the fluid replacement seems to be insufficient in the case of the selective cooling or when warming by means of the fluid replacement seems to be excessive in the case of the selective warming), the above means functions to decrease the temperature of the fluid replacement to be supplied. When the averaged temperature (Tav) is lower than the predetermined temperature of the object (T0) (that is, when Tavxe2x88x92T0 less than 0 or Tav/T0 less than 1, and thus for example when cooling by means of the fluid replacement seems to be excessive in the case of the selective cooling or when warming by means of the fluid replacement seems to be insufficient in the case of the selective warming), the above means functions to increase the temperature of the fluid replacement to be supplied. It is noted that when there is substantially no different extent (that is, when Tavxe2x88x92T0=0 or Tav/T0=1, and thus for example when the selective temperature controlling method seems to be working satisfactorily), the above means functions to keep the temperature of the fluid replacement to be supplied at that time.
Also, in an embodiment where the temperature of the diluted blood is changed after it has reached in the object the temperature of the object, and in an embodiment where a supply rate of the fluid replacement is too large, effects due to such embodiments are lowered in the apparatus of the second aspect.
Similarly to the apparatus of the first aspect as described before, the formation of a control system which obtains the averaged temperature (Tav) of the supplied fluid replacement temperature (T2) and the diluted blood temperature (T1), obtains the different extent between the averaged temperature (Tav) and the predetermined temperature of the object (T0), and controls the temperature and/or the supply rate of the fluid replacement to be supplied is well known to those skilled in the art.
In any aspect of the present invention, the diluted blood temperature or the averaged temperature of the diluted blood temperature and the supplied fluid replacement temperature is regarded as described above to represent and preferably be equal to the actual temperature of the object to which the selective temperature controlling method such as the selective cooling method is applied, and it is therefore preferable that the fluid replacement and the diluted blood are not so thermally affected by others as possible except the object. Thus, it is preferable that the temperatures of the fluid replacement and the diluted blood are measured as closely to the object as possible. Therefore, the temperatures of the fluid replacement and the diluted blood are measured at positions which are closest (namely, just vicinities) to the body. It is preferable that for example, the diluted blood is measured at a position which is immediately downstream of the outlet of the diluted blood from the inside of the body, and the supplied fluid replacement is measured at a position which is immediately upstream of the inlet of the supplied fluid replacement into the inside of the body.
In any aspect of the present invention, the withdrawn of the diluted blood and the supply of the fluid replacement are carried out through catheters as described below. In a particularly preferable embodiment, a thermister is located at one end of each of the catheters (one for the withdrawal of the diluted blood and the other for the supply of the fluid replacement) which end is closer to the body (i.e. the leading end when the catheter is inserted) or a vicinity of such end. Such catheters are inserted into the inside of the body so that the diluted blood temperature and the supplied fluid replacement temperature are measured while making the catheters located as near the object as possible to which the selective temperature controlling method is applied and the diluted blood temperature and the supplied fluid replacement temperature are measured, whereby the accuracy of the object temperature assumption is improved so that the accuracy of keeping the object at the predetermined temperature is improved.
In any aspect of the present invention, the apparatus according to the present invention comprises in a particularly preferable embodiment comprises a fluid replacement supply unit which cools or warms the fluid replacement to a temperature lower or higher than the body temperature and quantitatively supplies the fluid replacement into a blood vessel, a blood concentration unit which quantitatively withdraws the diluted blood from a blood vessel and concentrates the diluted blood preferably so as to reach a hematocrit value of at least 70% of that before being diluted (usually, a normal hematocrit value of a patient to whom the selective temperature controlling method is applied), and a blood supply unit which controls a temperature of the concentrated blood to a temperature near the body temperature and supplies the concentrated blood into a blood vessel.
When the selective temperature controlling method is applied using the apparatus according to the present invention, it is generally preferable to supply the fluid replacement which has been adjusted to the predetermined temperature (T0) beforehand upon starting to use the apparatus. Particularly, when the apparatus of the second aspect is used, since the supplied fluid replacement temperature (T2) is measured, it is preferable to control the temperature of the supplied fluid replacement such that T2 becomes the predetermined temperature (T0). Upon such control, it is desirable to take effects of various parameters (or factors, including a room temperature) into the consideration as described below.
In a case where the selective temperature controlling method is applied using the apparatus according to the present invention, it may be not preferable to rapidly change (for example cool or warm) the temperature of the object to the predetermined temperature (T0) when the predetermined temperature is greatly different from the temperature of the object before the application of the selective temperature controlling method (usually the body temperature in a normal condition). This is because the rapid temperature change of the object gives a certain shock, and for example electrolyte balance is broken, which may not be preferable. Thus, in such case, a manner is preferably employed in which a provisional predetermined temperature (T0-1) which is near the temperature before the application and which is between the temperature before the application and the predetermined temperature is set so that the temperature of the object reaches T0-1 first, then a next provisional predetermined temperature (T0-2) is set by shifting the provisional temperature toward the predetermined temperature a little so that the temperature of the object reaches T0-2, and then an additional next provisional predetermined temperature is set if necessary, . . . , and the temperature of the object finally approaches the original predetermined temperature (T0) in steps.
For example, in a case in which the object is to be cooled from 37xc2x0 C. to 25xc2x0 C. as the predetermined temperature (T0), the provisional predetermined temperature (T0-1) is first set at 35xc2x0 C. so that the object temperature reaches 35xc2x0 C., then the next provisional predetermined temperature (T0-2) is set at 33xc2x0 C. when the object temperature approaches or reaches 35xc2x0 C. so that the object temperature reaches 33xc2x0 C., . . . , whereby the object temperature thus approaches 25xc2x0 C. as the original predetermined temperature (T0) in steps. The manner in which the object temperature approaches the predetermined temperature may be stepwise as described above or continuous. When the object temperature is raised reversely, the above is applicable similarly. When the object is warmed, similar is applicable. It is of course possible to rapidly cool or warm if no problem occurs when the object temperature is changed to the predetermined temperature rapidly.
When the object temperature is adjusted to the predetermined temperature (T0) by applying the apparatus of the present invention to the selected object, in one embodiment a temperature of the fluid replacement to be supplied is controlled first by means of a fluid replacement temperature controller such that the temperature of the fluid replacement to be supplied becomes T0 (which may be the provisional temperature as the above). The fluid replacement thus controlled is supplied into the inside of the body.
When the apparatus of the first aspect is used for the supply of such fluid replacement, the diluted blood temperature (T1) is measured, and then the fluid replacement temperature controller which has been set at the predetermined temperature (T0) is re-set based on the measurement of the diluted blood temperature, that is the temperature of the fluid replacement to be supplied in the fluid replacement temperature controller is re-adjusted (namely, the temperature is set higher or lower than T0 or the temperature is kept). Also, when the apparatus of the second aspect is used, the supplied fluid replacement temperature (T2) is further measured followed by obtaining the average temperature of the supplied fluid replacement temperature (T2) and the diluted blood temperature (T1), and then the averaged temperature is compared with the predetermined temperature (T0) followed by controlling the fluid replacement temperature controller again. It is noted that with regard to the predetermined temperature (T0), it may be preferable to set a provisional predetermined temperature, based on which the fluid replacement temperature controller is adjusted followed by gradually shift the provisional predetermined temperature so that the original predetermined temperature is finally reached as described above.
After having made the object temperature reach the predetermined temperature, returning the object temperature to the original object temperature (that is, recovering the object temperature) truly corresponds to warming the object to the predetermined temperature. Therefore, the apparatus according to the present invention may be used for a temperature recovering method in which a temperature of the object is returned to its original temperature of the object which has been shifted to the predetermined temperature by the selective temperature controlling method. That is, the selective warming method after carrying out the selective cooling method or vice verse may be carried out by using the same apparatus.
It is noted in a case in which the object temperature is shifted to the predetermined temperature, and in particular the object is warmed, that it may be preferable to use oxygen containing blood when the object needs oxygen for the purpose of its metabolism. That is, it may be preferable that not using for example a Ringer""s solution as the fluid replacement, at least a portion and optionally most of the fluid replacement is replaced with blood (autologous blood or transfusion blood) as described below. When the blood is supplied as above, it is preferable that the blood is oxygen oxygenated by for example an artificial lung. In this embodiment, warming is applicable to a case in which the object is warmed from its normal temperature to a higher temperature as well as a case in which the object is returned from its selectively cooled temperature to its original normal body temperature.
It is noted that the present invention also provides an extracorporeal circulation method for the selective temperature controlling method. The former method is an extracorporeal circulation method for keeping an object at a predetermined temperature for the selective temperature controlling method, which comprises the steps of:
(A) quantitatively supplying (or metering) fluid replacement of which temperature has been adjusted into a blood vessel by means of a fluid replacement supply unit;
(B) quantitatively withdrawing blood diluted by the fluid replacement from a blood vessel and concentrating the withdrawn blood by means of a blood concentration unit; and
(C) controlling a temperature of the blood which has been concentrated and quantitatively supplying the blood into a blood vessel by a blood supply unit, and
the method being characterized in that a temperature of the withdrawn diluted blood is measured by means of the blood concentration unit, and a temperature of the fluid replacement which is quantitatively supplied by the fluid replacement supply unit is controlled based on a different extent between the measured diluted blood temperature and the predetermined temperature of the object.
The fluid replacement supply unit measures the temperature of the fluid replacement to be quantitatively supplied and may control the temperature of the fluid replacement based on a different extent between the predetermined temperature and an averaged temperature of the supplied fluid replacement temperature and the diluted blood temperature in place of the different extent between the measured diluted blood temperature and the predetermined temperature of the object.
Also, temperature control of the fluid replacement to be quantitatively supplied is preferably carried out while considering heat transfer between the fluid replacement and a surrounding of the apparatus until the fluid replacement is supplied into the blood vessel. In addition, it is preferable that the temperature of the fluid replacement to be quantitatively supplied has been adjusted to the predetermined temperature of the object when starting the above method. In other words, the present invention provides an extracorporeal circulation method in which the extracorporeal apparatus according to the present invention as described above or described in detail below is used.